1. Field of the Invention
The present invention relates to a micro/nano imprint mold of the fabricating process and the method of fabricating etching barrier pattern or anti-etch structure with high aspect ratio by utilizing thereof. More particularly, the present invention relates to a mold and the method thereof which are used to improve the accuracy of fabricated pattern and the pressure distribution among the substrate.
2. Description of the Prior Art
Light-emitting diode (LED) wafers will become epitaxial wafers by a fabricating process. The epitaxial wafers fabricating process comprises a MOCVD process. The growth of the materials is horizontally stacked, the defection rate of the lattice is low and the luminous rate of the light is high. To enhance the quality of the epitaxial layers, a designed pattern with high aspect ratio convex structure shall be formed on the substrate before the MOCVD process for producing the stacked epitaxial layers with less crystal dislocation and defect.
In the traditional semiconductor fabricating process, the mainstream is the lithography etching process. The lithography etching process is used to expose the photoresist coated on the substrate by the optical mask for forming the photoresist layer with a pre-determined shape to cover the substrate. Then, the substrate will be placed in an erosive gas or liquid. The parts of the substrate, which are not covered by the photoresist, will be etched and form a notch structure. When the erosion develops to a certain level, the photoresist layer can be removed by the solvent and form the convex structure.
However, the lithography etching process has the following disadvantages. (1) The photoresist with high resolution is expensive. The price of photoresist can be reach hundreds of thousands of US Dollars per liter so that the cost of the lithography etching process is high in prior art. Additionally, because the less selection of the material, it is difficult to meet the need of the different etching process. For example, the anti-etching ability of the photoresist of the PMMA is poor. (2) The lithography etching process uses an aligner exposure machine to expose all substrate or a stepping exposure machine to expose the small area of the substrate. Using the aligner exposure machine to expose all substrate is fast, but the resolution of the lithography etching process is limited (line width shall be larger than 2 μm). Using the stepping exposure machine to expose the small area of the substrate can fabricate the structure with small line width. So that the photoresist with low anti-etching ability and thin-film thickness shall be used, the etching structure with high aspect ratio is difficult to fabricate. (3) The anti-etching ability of the photoresist is limited, particularly the photoresist which is used in the lithography process with high resolution. Because the ability of the anti-etching ability is poor, the yield is low when the micro/nano structure with thinner line width is fabricated in the lithography etching process.
Accordingly, the micro/nano imprint fabricating process is developed. The micro/nano imprint fabricating process is used to imprint the substrate directly so that the expected pattern can be imprinted directly. However, when the flatness error of the substrate cannot be accepted, the micro/nano imprint fabricating process cannot imprint the pattern on the substrate smoothly and unevenly. Thus, the yield will be decreased.
Furthermore, in traditional micro/nano imprint fabricating process, the structure of the sticky and flexible material will become highly different because of the uneven pressure. Please refer to FIG. 1. FIG. 1 illustrates a perspective view of the non-uniformity of fabricated structures according to the prior art. As shown in FIG. 1, the peripheral of the material layer will lower than the height of the central material layer because the pressure applied to the material layer by the center of the mold is larger than the pressure applied by the peripheral of the mold. Thus, the phenomenon will affect the quality of the fabricating process.
Therefore, it is necessary to provide a micro/nano imprint mold of the fabricating process which is used to improve the flatness with large errors and the uneven pressure among the substrate.